The superfamily of 5-HT serotonin receptors includes 7 classes (5-HT1-5-HT7) which encompass 14 subclasses [D. Hoyer, et al., Neuropharmacology, 1997, 36, 419]. The 5-HT6 receptor is the latest serotonin receptor identified by molecular cloning both in rats [F. J. Monsma, et al., Mol. Pharmacol., 1993, 43, 320; M. Ruat, et al., Biochem. Biophys. Res. Commun., 1993, 193, 268] and humans [R. Kohen, et al., J. Neurochem., 1996, 66, 47]. Compounds that show affinity for 5-HT6 receptors are suitable for the treatment of several disorders of the central nervous system and the gastrointestinal tract, such as irritable bowel syndrome. Compounds with affinity for 5-HT6 receptors are also suitable for treating anxiety, depression and cognitive memory disorders [M. Yoshioka, et al., Ann. NY Acad. Sci., 1998, 861, 244; A. Bourson, et al., Br. J. Pharmacol., 1998, 125, 1562; D. C. Rogers, et al., Br. J. Pharmacol. Suppl., 1999, 127, 22P; A. Bourson, et al., J. Pharmacol. Exp. Ther., 1995, 274, 173; A. J. Sleight, et al., Behav. Brain Res., 1996, 73, 245; T. A. Branchek, et al., Annu. Rev. Pharmacol. Toxicol., 2000, 40, 319; C. Routledge, et al., Br. J. Pharmacol., 2000, 130, 1606]. It has been shown that typical and atypical antipsychotic drugs used to treat schizophrenia have a high affinity for 5-HT6 receptors [B. L. Roth, et al., J. Pharmacol. Exp. Ther., 1994, 268, 1403; C. E. Glatt, et al., Mol. Med., 1995, 1, 398; F. J. Mosma, et al., Mol. Pharmacol., 1993, 43, 320; T. Shinkai, et al., Am. J. Med. Genet., 1999, 88, 120]. Compounds with affinity for 5-HT6 receptors are also suitable for treating infantile hyperkinesia (ADHD; Attention Deficit/Hyperactivity Disorder) [W. D. Hirst, et al., Br. J. Pharmacol., 2000, 130, 1597; C. Gérard, et al., Brain Research, 1997, 746, 207; M. R. Pranzatelli, Drugs of Today, 1997, 33, 379]. It has also been shown that 5-HT6 receptors also play a role in the intake of nutrients [Neuropharmacology, 2001, 41, 210-219]. Eating disorders, particularly obesity, are a serious and growing threat to public health in all age groups, as they increase the risk of developing other more serious diseases that endanger the life of patients, such as diabetes or coronary diseases.
Several patent documents refer to compounds with affinity for receptors of the 5-HT superfamily. Documents WO 96/23783, WO 96/02537, WO 96/11929 and WO 97/08167 describe heterocyclic compounds antagonists of 5-HT2b/2c receptors.
On another hand, there are other patent documents that have described indene derivatives with therapeutic activity. U.S. Pat. No. 5,092,827, U.S. Pat. No. 6,025,394, U.S. Pat. No. 5,958,982, U.S. Pat. No. 5,965,619, U.S. Pat. No. 6,028,116, US 2001/0006965 and US 2001/0020020 describe indene derivatives as being suitable for treating psoriasis, acne, sarcoidosis, pre-cancerous lesions and neoplasias, as well as diabetic retinopathy and macular degeneration. The therapeutic effect of these compounds seems to originate in their inhibitive action on a specific phosphodiesterase of cGMP (cGMP PDE), as described in the U.S. Pat. No. 6,177,471.
Surprisingly, the authors of the present invention have observed that indene derivative compounds with general formula (I) show an affinity for 5-HT6 receptors ranging from good to excellent. These compounds are therefore particularly suitable as pharmacologically active agents in medicaments for the prophylaxis and/or treatment of disorders or diseases related to 5-HT6 receptors.